Businesses, particularly small to medium size offices, typically have a need for a variety of voice and data communications. For example, a typical office might have a dedicated fax machine, using a dedicated or shared telephone line, one or more telephone lines for voice communications, perhaps coupled to a central or distributed voice mail system(s), and one or more computers or computer networks, often coupled to telephone lines via one or more modems. Many offices now use the Internet in some form for business communications or research or the like, often by way of a modem or modem pool coupled to individual computers.
Typically, such business communication needs have been fulfilled with piecemeal technical solutions, typically from separate equipment and service vendors, and with separate hardware, software and design considerations. FIG. 1 illustrates a conventional small office communication configuration. Voice communication system 1 typically is implemented by way of multiple analog trunks 16 from wide area network (“WAN”) 18. WAN 18 often consists of a telecommunication network by way of a local telephone company or other telecommunications service provider. Analog trunks 16 may be directed through switching system 10, which may be a conventional PBX or similar telephone switch. Telephones 12 and voice mail system 14 are coupled to switching system 10. Often, dedicated analog line 16A is coupled to facsimile 44 for facsimile communications.
Data system 2 typically is implemented with a plurality of computers (or workstations, etc.) 24 interconnected by way of packet network 26, which may be a standard Ethernet compliant network or other office network. Network 26 often is coupled to remote access server 32, which is connected to one or more analog trunks 40, and which may include one or more modems in a modem pool. Computers 24 may communicate with remote systems via the modem pool of remote access server 32 over analog lines 40 and WAN 42. Network 26 typically includes a connection to printer 22 and file server 20. In more sophisticated systems, network 26 may be coupled to switching hub 28 and router 30, which is coupled to WAN 42 over digital trunks 38. Data system 2 also may include a connection between one or more of computers 24 to modem 36, which in term is coupled to WAN 42 over dedicated analog trunk 40A.
Such a conventional system often is characterized by piecemeal equipment and network solutions, limited or non-existent coordination and management between voice system I and data system 2, non-optimized or non-integrated equipment, and inefficient use of costly network services (telephone lines, data lines, etc.), such as duplicate and often idle phone and data network lines, often provided from multiple equipment/service providers. In general, such conventional systems are neither constructed nor operated in a manner to provide efficient and integrated voice/data communications.
Moreover, PBXs and other telephony systems coupled to multiple telephones or similar telephony devices typically interface with such devices through what are often referred to as “station cards.” Such devices may be analog or, more recently, digital. Such cards typically must supply several DC and/or oscillating voltages to the telephony devices in order for the devices to operate properly.
Traditionally, such voltages have been supplied in a more or less centralized manner, with a central power supply. Examples of such conventional systems are illustrated in FIGS. 6 and 7. Conventional system 110 of FIG. 6 includes a plurality of station cards 116, to which are coupled a plurality of telephone lines 118. A plurality of telephony devices 120 (such as conventional analog or digital telephones) are coupled to telephone lines 118. Central power supply 112 is included in system 110 in order to supply a plurality of DC and/or oscillating voltages to station cards 116 in a centralized manner over bus 114. For example, with conventional analog type telephones, bus 114 may provide DC voltages of −24 volts and −48 volts, and an oscillating waveform for ringing of the telephones.
The conventional system of FIG. 7 includes a plurality of station cards 126 coupled to central power supply 122. Station cards 126 include subscriber line interface circuit (or “SLIC”) 128, such as the Am79R79 Ringing Subscriber Line Interface Circuit manufactured by Advanced Micro Devices, Inc. (the data sheet for which is hereby incorporated by reference). SLIC 128 receives various DC voltages, such as −24 volts and −70 volts over bus 124, and also receives a TTL level clock. Because SLIC 128 may generate a ringing voltage internally from the −70 volts, bus 124 need not supply such an oscillating ringing voltage to station cards 126. SLIC 128 provides appropriate DC and oscillating voltages, as required, to analog processing circuit 130, which in term is coupled to RJ interface 132. A variety of telephony devices 136 are coupled to RJ interface 132 via telephone line 134.
As with the embodiment of FIG. 6, however, power supply 122 is centrally arranged and provides a central source of power for the plurality of station cards 126. Power supplies 112 and 122 typically must be designed to support the maximum number of station cards that the system is designed to handle in order to avoid having to upgrade the power supply as station cards are added. Thus, such centrally provided power supplies tend to be larger, more costly, and consume more power than is required for a typical application. Such centrally provided power supplies also tend to provide a single point of failure, and also tend to dissipate substantial heat in a single location. Furthermore, such power supplies tend to provide limited fault tolerance, diagnostics and system configuration flexibility.